﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Linq.Expressions;

namespace Epic.Data.Expressions
{


    internal static class InnerExpressionHelper
    {


        public static Expression<Func<T, bool>> True<T>() { return f => true; }
        public static Expression<Func<T, bool>> False<T>() { return f => false; }

        public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> expr1,
                                                            Expression<Func<T, bool>> expr2)
        {
            if (expr2 == null) throw Error.ArgumentNull("expr2");
            if (expr1 == null) return expr2;
            var invokedExpr = Expression.Invoke(expr2, expr1.Parameters.Cast<Expression>());
            return Expression.Lambda<Func<T, bool>>
                  (Expression.OrElse(expr1.Body, invokedExpr), expr1.Parameters);
        }

        public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> expr1,
                                                             Expression<Func<T, bool>> expr2)
        {
            if (expr2 == null) throw Error.ArgumentNull("expr2");
            if (expr1 == null) return expr2;

            var invokedExpr = Expression.Invoke(expr2, expr1.Parameters);
            return Expression.Lambda<Func<T, bool>> (Expression.AndAlso(expr1.Body, invokedExpr), expr1.Parameters);
        }

        public static Expression<Func<T, bool>> Not<T>(this Expression<Func<T, bool>> expr)
        {
            var not = Expression.Not(expr.Body);
            return Expression.Lambda<Func<T, bool>>(not, expr.Parameters);
        }
    }
}
